Direct bandgap silicon quantum dots achieved via electronegative capping

TL;DR

This paper introduces a method to create silicon quantum dots with significantly enhanced radiative rates by surface engineering with electronegative ligands, potentially enabling direct bandgap-like optical properties.

Contribution

It presents a novel surface engineering approach to transform silicon quantum dots into structures with direct bandgap-like radiative properties, supported by tight-binding simulations.

Findings

Radiative rates increased by over two orders of magnitude.

Surface electronegative ligands alter electron density and conduction band levels.

Potential realization through covalent electronegative surface coatings.

Abstract

We propose a novel concept of achieving silicon quantum dots with radiative rates enhanced by more than two orders of magnitude up to the values characteristic for direct band gap semiconductors. Our tight-binding simulations show how the surface engineering can dramatically change the density of confined electrons in real- and $k$-space and give rise to the new conduction band levels in $\Gamma$-valley, thus promoting the direct radiative transitions. The effect may be realized by covering the silicon dots with covalently bonded electronegative ligands, such as alkyl or teflon chains and/or by embedding in highly electronegative medium.